Anaheim,
CA (1/25/99)- The humble soy bean contains potent anti-cancer and anti-pain
capabilities, report researchers at the annual meeting of the American Association
for the Advancement of Science.
Right: Baked
Thai-style Tofu Brochettes
Researchers at Wake Forest University reported the results of series of studies
with post-menopausal monkeys. When the monkeys received estrogen replacement
therapy, precancerous cell proliferation was observed in mammary glands and
in endometrial tissue. This was expected. Then the monkeys were fed a diet
including plenty of soy products. The precancerous cell changes stopped shortly
thereafter.
"These data indicate that soy supplements may decrease breast and endometrial
cell proliferation and therefore could decrease cancer risk in these tissues,"
reported J. Mark Cline, D.V.M., Ph.D., assistant professor of comparative
medicine, Wake Forest University.
Cline believes that the the soy protein mimics the action of progestin, which
also slows cellular proliferation and is known to reduce cancer risk. he emphasized
that much research remains to be done to better understand how soy protein,
which contains plant estrogens called phytoestrogens, exerts these actions.
It is likely that the amount of phytoestrogens is important for the overall
effect. In another study involving rats whose ovaries had been removed, the
soy proteins did not cause an increase in cell proliferation either in the
uterus or mammary gland tissues. However, when the animals received low doses
of estrogen replacement therapy, the soy estrogen appeared to cause an increase
in cell proliferation in breast tissue. Yet at a higher dose of estrogen replacement
therapy, the soy diminished the cell proliferation in both the uterus and
breast.
"At some dose combinations, the two are additive, and at other dose combinations,
they are antagonistic. Widespread consumption of phytochemicals in the human
diet and as supplements make it imperative that we understand their effects,
particularly as they related to differing developmental and functional stages
of the breast," Cline said.
Studies of human populations show a lower incidence of breast cancer in Asia,
where diets contain higher amounts of soy protein. Recent studies have shown
that American-born children of Asian immigrants have a 60 percent higher risk
of developing breast cancer than do native Asians who immigrate to America.
"This implies that the breast-cancer protective effect may occur early in
life. The benefit of soy phytoestrogens is clearer for dietary exposures early
in life and for pre-menopausal women. The benefit for older women and breast
cancer survivors remains to be determined," he said.
Pain Relief
In a recent issue of the journal Neuroscience Letters, researchers
at Johns Hopkins University reported that laboratory rats fed a diet high
in soy protein develop far less pain after nerve injury than their counterparts
on soy-free diets.
"In people, strong individual differences exist in the perception of pain.
And while this is undoubtedly due to a number of factors, the idea that diet
could affect the pain experience offers fascinating possibilities for understanding
our vulnerability to it. Similarities do exist between rats and humans in
the biology of pain perception," says Hopkins neurosurgeon James N. Campbell,
M.D.
The finding came about accidentally. The researchers were developing an
animal model of a phenomenon seen in humans, where pain sensitivity increases
following nerve injury. Conflicting results with colleagues in Israel led
the investigators to check every aspect of the protocol. Finally, they realized
that the only difference had been what was in the food bowl.
It turned out that the rat chow used in the American side of the protocol
had a lot more soy protein than the Israeli chow. When the American rats were
fed the soy-free diet, their sensitivity to pain also returned.
The next step will be for the researchers to investigate which component
of soy meal suppresses sensitivity, and how it does this. That research could
help explain individual differences in pain sensitivity, and might lead to
new therapies, said Campbell.
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